This invention relates to methods of manufacturing tanks with agitation portions and tank trailer systems having a main tank and lateral support tanks. Trailer or skid mounted tanks are utilized in different industries such as asphalt sealing and hydro seeding. Efficient manufacture and assembly of these trailer tank combinations are needed.
With regard to asphalt sealing equipment, asphalt is comprised of essentially two components, aggregate and binder. The aggregate is a measured mixture of stone and sand while the binder is a petroleum derivative. The components are combined, heated and blended in a batch plant. The area where asphalt is to be laid is first prepared by grading and compacting the dirt. Gravel is laid on this area and compacted to a thickness of six to ten inches. The hot asphalt mix is then spread over the area and compacted to a uniform thickness of two to four inches.
As soon as new asphalt is laid, the binder begins to evaporate and decay as it is exposed to the damaging effects of the sun (oxidation), rain and snow. Gasoline, oil leaks and chemicals such as road salts can also have a dramatic effect on the life of the binder. As the binder is destroyed by these external factors, its ability to hold the aggregate together diminishes. This problem takes the form of cracks, distortion and disintegration of the asphalt surface. After three to five years under normal conditions, major deterioration has taken place.
Asphalt sealcoat liquid is a viscous brownish liquid that is applied in a thin layer to asphalt surfaces to protect same from deterioration. Sealcoat preserves the elastic and adhesive characteristics of the asphalt binder by sealing out the oxidizing effects of the sun, salts, and deteriorating effects of water and petroleum spillage. Sealcoat also dries to an attractive uniform flat black color creating a like new appearance. Sealcoat can also be mixed with sand to create a non-skid surface with increased wear characteristics. Sealcoat can also reduce loose stone on an asphalt surface. Generally, asphalt sealcoat is a highly economical method of maintaining and extending the life of asphalt surfaces.
The most common asphalt sealcoat is a water base solution of refine coal tar emulsion, gypsum, clay, and silica. Other additives are available to enhance particular characteristics of the sealer such as the adhesion characteristics, drying time, sand suspension, and the color of the sealer. Prior to application of the sealcoat, it is very important to have the asphalt liquid properly mixed and agitated.
Where an asphalt surface being covered is of substantial square footage it is very difficult to manually mix and agitate large quantities of the sealcoat liquid. Commercial applicators include a self-propelled piece of equipment with a hydraulically agitated tank, an associated pumping system for spraying the sealcoat onto the asphalt surface, and a series of squeegees on the machine. As the operator drives the machine forward, the squeegees drag across the surface leaving a thin, evenly applied layer of sealer on the asphalt. This type of equipment is very expensive and is difficult to use in confined areas.
Additionally, trailer mounted sealcoat application systems are known. Such systems include a large tank of two hundred gallons or more installed on the trailer along with ancillary equipment. The fluid in the tank is pumped through a hose and a spray nozzle for spray application of the sealcoat. Supplemental brushing or use of a squeegee may be performed as desired. It is particularly important with these relatively high quantities of sealcoat liquid that the liquid be properly agitated within the tank. Prior art tanks were typically constructed of steel. Also rotary molded tanks are known in which the agitation portion is assembled inside the blow molded drum through the top access opening. This type of assembly is tedious, time consuming, and difficult.
Fasteners such as inserts with threaded bores or the like which may be attached to the rotary mold portions prior to the mold process are known. Such fasteners are typically exposed at the outer surface of the tank after the molding process.
In industries other than asphalt sealcoating, large agitation tanks are also utilized to maintain slurries and proper agitation of fluids. For example, the hydroseeding industry in which seeds such as grass seed is sprayed from a nozzle onto a lawn to be seeded. Also in the earth drilling or boring industry, drilling fluid commonly known as mud is mixed from bentonite and must be constantly agitated and recirculated to maintain its desirable characteristics. In each of these industries the tanks are typically assembled from several components and agitation equipment is either assembled in the tank after the tank is completed or near completion or the parts are after partial assembly of the tank. Both of these industries would benefit from a tank with agitation means and capabilities that is more easily manufactured, less complicated, and easier to clean and maintain.
A need exists for a tank trailer system with several tanks mounted thereon in an efficient manner. Further, a multi tank trailer tank system that is relatively inexpensive to manufacture would be desirable.
In a preferred embodiment, an apparatus requiring storage of a liquid that needs agitation includes a plastic tank that is rotationally molded around an agitation portion. Additionally, lateral support tank side wall with a curvature that follows the curvature of the tank may be rotationally molded and be utilized as auxiliary tanks. The tank and auxiliary lateral support tanks are mounted on a trailer deck such as a skid or trailer. Various embodiments of the apparatus may be utilized in specific applications such as asphalt sealcoat applicators, hydroseed applicators, and bentonite or mud mixing apparatuses for earth drilling equipment.
An object and feature of the invention is that the lateral support tanks provide excellent lateral support for the main tank as well as providing additional tanks utilizing a minimizing amount of trailer deck surface. The asphalt sealcoat application system has such a plastic rotary molded tank mounted on a powered vehicle or trailer and utilizes a pump connected to a hose and spray wand for application of sealcoat on an asphalt surface. The tank is preferably formed of polyethylene resin and the agitation portion includes a plurality of paddles and a shaft extending from the interior of the tank for mixing the sealcoat liquid. The polyethylene tank is rotary molded around the assembled agitation portion. The invention includes the methodology of molding the tank, a tank molded by said methodology, and the apparatus for accomplishing said methodology.
The internal mold periphery and thus the finished molded tank is generally shaped as elongate cylinder. The agitation portion comprising a shaft extending coaxially with the axis of the tank is placed in the interior of the mold portions. After the mold process the shaft extends out both ends of the completed molded tank. Appropriately spaced threaded fasteners positioned around the exit of the shaft from the tank allow the fastening of a seal and bearing.
An advantage and feature of the invention is that the plastic rotationally molded tank is more economically manufactured than conventional plastic tanks.
A further advantage and feature of the invention is that the agitation portion may be unitary and integral, such as by welding, within the integral plastic tank which may have a very restricted tank opening. This provides for less maintenance and less failures of the agitation portion. Previous agitation portions placed in such integral plastic tank were assembled inside the tank after molding with fasteners such as nuts and bolts. The absence of nuts and bolts that hold the components of the agitation portion together minimizes excessive accumulation of sealcoat on the agitation portion.
A further advantage and feature of the invention is that the method may be used for multiple shafts each with separate agitation members extending from a single integral tank.
A further advantage and feature of particular embodiments of the invention that utilize the plastic saddles is that the saddle structure provides both a secure and robust constraint for the tank as well as providing auxiliary fluid tanks.
A further advantage and feature of particular embodiments of the invention is that the principal fluid storage components as well as the fluid agitation components of a asphalt sealing apparatus may all be rotationally molded providing durability and a relatively low manufacturing cost.